Refined sugar

Supersweet foods, such as those containing refined sugar can lead to spikes in insulin levels which, in turn, can lead to fluctuations in blood sugar.

Although this might not directly affect your stomach, it could make you feel clammy and shaky, which isn't going to improve your overall state, says Robynne Chutkan, MD, assistant professor in the division of gastroenterology at Georgetown University Hospital in Washington, DC.

Dairy

Dairy products such as milk and cheese top the list of "don't” foods when it comes to upset stomachs. For one thing, more than half the world's population is already lactose intolerant, meaning they lack the necessary enzyme to digest dairy products.

But even if you're not lactose intolerant, a viral or bacterial infection can affect lactase (the lactose-digesting enzyme) and could cause you to temporarily or even permanently lose your ability to digest lactose, says Dr. Chutkan.

Chocolate and caffeine

One of the main reasons caffeine and chocolate (which may contain caffeine) are irritating to an already-upset tummy is that, like peppermint tea, they relax the lower esophageal sphincter, which allows acid reflux.

Caffeine can also loosen stools, which isn't good if you already have diarrhea. And chocolate that contains milk products or nuts could be difficult to digest for those who are lactose-intolerant or allergic.

Spices

Spices and spicy food may not be as bad as you think. "If you're used to eating spicy food, you probably have a very good tolerance for it and it will be fine," says Dr. Chutkan.

If you're not used to these foods, this may not be the time to start. But also pay attention to howand with whatthe spices are cooked. "Spices are associated with cooking in oil, so fat is probably more a reason [for upset stomach] than the spice itself," says Amit Bhan, MD, service chief of gastroenterology at Henry Ford Health System, in West Bloomfield, Mich.

Processed foods

Not unlike sodas, processed foods with a long-shelf life typically have a lot of
chemicals, including preservatives, which could further upset your tummy.

So while a can of spaghetti might look attractive because it's sitting right there in your pantry, you may want to leave it alone for now. (The tomato sauce would probably be bad for your stomach anyway.)